For example, a centrifugal compressor is used to compress a processing gas in various plants. In the centrifugal compressor, a processing gas taken into an intake volute from an intake nozzle is compressed in a flow channel of an impeller that rotates together with a rotation shaft, and is then discharged from a discharge nozzle.
Here, as a structure of the intake volute of the centrifugal compressor, for example, as shown in FIG. 5 in Patent Literature 1, a flow split type structure in which a processing gas taken from an intake nozzle flows through two divided paths, the left and right paths, along a casing is known in the related art.